Like pdhenry, never at an airport, but in my case at the Philadelphia railroad station.

I had taken the train into town to interview for a camp counselor job. (This was a long time ago.) The evening interview ran longer than expected. By the time I got back to the station the last train back to college had left. Like a typical college student I didn't carry enough money for a hotel and in those days had barely heard of credit cards, let alone having one. All I had was the second half of a round trip ticket. I put a note on the bench next to my head "please wake me at 6:30," in time for the first morning train, and went to sleep. I slept pretty well - ah, to be young again - and was shaken gently at 6:30 by an elderly African-American man. Got on the train and made it to my first class.